Special relativity

Something is still not clear to me. As far as I understand, even before Einstein, it was assumed that the laws of physics were the same in all reference frames. So what's new here “in terms of the solution“? (I'm not asking about the second principle of the constancy of the speed of light).

True, but they didn't understand that for this to happen, the space-time transformations between different reference systems had to be changed.

The question is what are the laws of physics.
Something that depends on the observer's point of view is not a physical law and cannot be said to exist. For example, the electric field (which becomes magnetic as a function of speed) does not exist. And this is a novelty.

I haven't gotten to the bottom of your point yet. This is not a criticism, but really something I don't understand yet.
As far as I understand, even in Newtonian physics there are laws of transformation between different reference systems. If I'm right and if, as you explained here, the principle is that the laws of physics are the same in all reference systems, then there is nothing new here from a methodological point of view in principle.
Where am I wrong?

This principle is Galileo's, not Einstein's.
What Einstein innovated was about the speed of light, which is constant in all inertial systems, and from this it follows that time and space are relative. And this is new and inconceivable.

Doron

Indeed, in terms of what you call the first principle, there was no innovation here. The innovation is that in order for it to fit with the second principle, one must give up Galileo's transformations (which are intuitive according to our eyes) and adopt the Lorentz transformations, which are a great innovation (meaning that in systems that are relatively fast, time does not move at the same rate (in one it moves slower than in the other), and the lengths of the same objects take on a different value in each of these systems (the same table can have a length of 2 meters in one and 3 meters in the other)).

In fact, the Lorentz transformations are not Einstein's innovation either. They are Lorentz's, who conceived them so that Maxwell's equations (the electromagnetic equations) would have the same form in systems that move at a speed relative to each other. Only he assumed the existence of the ether for this (the existence of a medium in which these waves travel and which fills the entire space. This is so that the transformations would fit the Newtonian mechanical picture of the world that existed until then). Einstein managed to derive them from the two principles you mentioned without any connection to Maxwell's equations and without assuming the existence of the ether (for which there was no evidence of its existence and whose existence also created some problems). He showed that it is a property of mechanics and not just of electricity and magnetism. In other words, it is something more general and universal. Therefore, the Newtonian mechanical picture of the world is incorrect. This was the great innovation.

Thank you for the answer. I thought about it.

Emanuel (and others)
So we can summarize and say something like this: Einstein's fundamental methodological innovation in terms of the constancy of the laws of physics is actually their extension to mechanics as well. While before Einstein they believed in constant regularities regarding certain fields (electromagnetism, etc.), from the moment Einstein entered the picture, a way to generalize different fields was discovered.
Right?
If that is indeed the case, it fits in perfectly with the philosophical principle that Einstein planted in his physics background (the centrality of postulation).

The great innovations are not about methodology, but about the destruction of old beliefs. Basic human worldviews that are not in line with reality.

The fact that the speed of light does not change (and therefore from this assumption it follows that time and space are connected and dependent on each other and can change) is contrary to the way we experience the world.

And for evidence. His big mistake was that he did not destroy the old belief that the stars do not move.

Old beliefs are an elusive thing.